Electron discharge device



INVENTOR TREVOR 62/1/7/1 ATTORNEY Y B Y T H CLARK ELECTRON DISCHARGE DEVICE Filed April 11, 1941 Dec. 22, 1942.

atented Dec. 22, 1942 ELECTRON DISCHARGE DEVICE Application April 11, 1941, Serial No. 388,035 In France November 5, 1940 3 Claims.

The invention relates to ultra high frequency discharge devices, and more particularly to electron discharge devices that employ velocity modulation of an electric beam.

In a general way, the object of the present invention is to determine the conditions under which such an optimum performance can be effected.

More particularly, in an electron discharge device in which an electron beam is modulated in velocity in the known manner by first passing through a very short oscillatory electromagnetic field in its path of travel, and then passing through a space without variation of electromagnetic field to another oscillatory electromagnetic field that is also of very short length, the invention provides means for varying the transit time of the electrons in space without variation of the electromagnetic field, and in a manner that is independent of any concentration action on the beam or of any variation of the density of the beam, and accordingly of the intensity of the current it carries. This is done in a simple manner without any noteworthy complication in the structure of the device, and without introducing any change in the impedance of the oscillatory circuits.

For modifying the transit time of the electrons, it has indeed already been proposed to vary the potential applied between the cathode and the tuned oscillatory circuits, but this method results in a variation of the current coming from the cathode, which must be compensated by applying suitable voltages on intermediate electrodes. The presence of such intermediate electrodes makes the unit more complicated and. its operation more unreliable. It has also been proposed to vary the transit time of the electrons by acting on the customary concentration electrode of the electrons. Such use of the one same electrode for concentrating a beam and controlling the current intensity results in the concentration of the beam varying with the current intensity, and this is particularly undesirable.

On the contrary and in accordance with certain characteristic features of the invention, a noteworthy variation of the transit time of the electrons in space without variation of the electromagnetic field may be controlled, without having to bring about any change either in the concentration of the beam or in its current density, by placing in this novariation space of the electromagnetic field an independently controlled electrode for retarding or accelerating the electron beam as a whole.

The invention is explained in detail in the following description, with reference to the appended drawing, in which:

Fig. 1 shows a section taken along the longitudinal axis of an oscillatory circuit for an electron velocity modulation device which is associated to a means for controlling the beam according to characteristic features of the invention;

Fig. 2 is a sectional view in elevation of a part of the oscillatory circuit of Fig. 1;

Fig. 3 shows a sectional view of the oscillation structure taken on line 33 of Fig. 1;

ig. 4 illustrates schematically in perspective a modification of the design of Figs. 1 and 3.

For greater simplicity, the drawing shows the devices used for generating and collecting the electron beam that traverses the oscillatory circuit only diagrammatically, because such devices may be of various well-known types and do not .per se form an essential part of the present invention.

The design of the oscillatory circuit selected as an example and shown in Figs. 1 to 3 comprises two resonant volumes A and B defined two terminal walls i of similar construction and symmetrically disposed. which fit into a cylinder and a center wall 3. An axial conduit C is defined by cooperating tubular rims 65' of walls ll' and l of wall Within the portion of the conduit C that is defined by the tubular rim 7 there is installed a cylinder 4 which serves to modify the speed as a whole of the electrons of the beam in a manner explained further on.

These same elements are also shown in the perspective view in Fig. 4. However, this Fig. 4 shows the conduit i as having a uniform straight section over its entire length, the tubular rims l and l and the electrode 4 having the same section and the tubular rim i being of greater size.

The tubular electrode 4 is preferably supported by elements uniformly distributed over its periphery in order to insure precise centering. Furthermore, in order to retain the electrical symetry of the design, the potential applied to this electrode s, which may be supplied by a single conductor, is preferably supplied by as many conductors as there are supports. One example of an embodiment is shown in Figs. 2 and 3 of the drawing, and in these each supply connection 5 is surrounded by an insulating tube 8 of suitable thickness for supporting the difference in potential between electrode 4 and the oscillatory circuit. In the case shown in the drawing there are three potential leads insulated in this way at 120 to each other.

The operation of devices like those described above as examples is explained as follows: the electron beam generated by a suitable cathode l and concentrated by an electrostatic or electromagnetic electronic optical system H is accelerated by the positive potential applied to the body of the oscillatory circuit in such a way as to pass along the central conduit C. On leaving the conduit it is taken up by an electrode or a collector assembly I2 positioned for this purpose. These devices for generating and taking up the electron beam are not described in detail since numerous suitable arrangements may be found.

When there is an oscillatory circuit in the circuit into which the beam first enters, e. g., the circuit A in the drawing, there will occur a modulation of the velocity of the beam in the known manner on its passage that is the gap between 6 and 1. In the following no-variation space of the electromagnetic field within the tubular rim 1, this modulation of speed is transformed into a modulation of intensity by electron grouping and, when the beam modulated in intensity passes through the second discontinuity between 1 and 6', a high frequency current will be induced in the second circuit B. Since this mode of operation is well known per se it will not be further described in detail,

However, in order to effect optimum operation, it is necessary to be able to modify the transit time between the two discontinuities or control points. This adjustment can be made in a simple manner in devices that incorporate features of the invention by modifying the potential of electrode 4 with respect to the rest of the circuit considered as a whole. The beam is consequently accelerated or retarded in its entirety in such a way as to insure the optimum transit time. It can be seen that the density of the beam is not affected by this modification of the potential,

but that the current or electronic density of the beam is wholly determined by the potential applied to the body of the oscillatory circuit. By effecting suitable insulation of electrode 4 and its lead-in connection, e. g., by using quartz tubes 8 or other supporting means that provide suitable spacing of electrode 4 and its connections 5, the system in accordance with the present invention may be arranged to permit application of a difference of several hundreds of volts between electrode 4 and the body of the oscillatory circuit and consequently bring about considerable variation of the transit time of the electrons.

Furthermore, the impedance of the beam can in this way be adjusted to the impedance ofiered by circuit B and this is important for producing optima conditions of output. This can be effected without either changing the concentration of the beam or its current density, or else by modifying the current density without modifying the transit time in the no-variation space of the electromagnetic field. The invention consequently provides means not only for the operation of the device at optimum efiiciency but also for determining the conditions of this optimum operation.

Although the invention has been described for certain particular examples of embodiment as described and illustrated, it is evident that it is by no means limited thereto, but is on the contrary capable of numerous modifications and adaptations without departing from its scope.

What is claimed is:

1. A velocity modulation type electron discharge tube, comprising means for velocity modulating beam of electrons, means positioned in the path of said beam in advance of said first mentioned means for allowing said velocity modulated electrons to form into groups, means for extracting energy from said grouped electrons positioned in the path of said beam in advance of said second named means and means for controlling the transit time of the electron beam comprising a control electrode mounted within said second named means, and lead in means for applying a predetermined potential to said electrode.

2. A tube according to claim 1, wherein said second named means provides a shielded space between said first and third named means, and said electrode comprises a hollow cylinder within said shielded space.

3. A tube according to claim 1, wherein said controlling means comprises a hollow electrode, and conductor means insulated from the other portions of the tube and symmetrically spaced with respect to said electrode and connected thereto.

TREVOR H. CLARK. 

